Titania-doped zirconia as platinum group metal support in catalysts for treatment of combustion engine exhausts streams

ABSTRACT

Composites of mixed metal oxides for an exhaust gas purifying catalyst comprise the following co-precipitated materials by weight of the composite: zirconia in an amount in the range of 55-99%; titania in an amount in the range of 1-25%; a promoter and/or a stabilizer in an amount in the range of 0-20%. These composites are effective as supports for platinum group metals (PGMs), in particular rhodium.

TECHNICAL FIELD

The present invention is directed to a mixed metal oxide support for anexhaust gas purifying catalyst and methods for its use. Moreparticularly, provided are titania-doped zirconia supports for aplatinum group metals (PGMs). Specifically, titania-zirconia supportswith optional additions of promoters, such as lanthana, or stabilizers,support rhodium for providing excellent three-way conversion (TWC)catalytic activity at low temperatures (for example below 350° C. orbelow 400° C.).

BACKGROUND

Emission standards for unburned hydrocarbons, carbon monoxide andnitrogen oxide contaminants continue to become more stringent. In orderto meet such standards, catalytic converters containing a three-wayconversion (TWC) catalyst are located in the exhaust gas line ofinternal combustion engines. Such catalysts promote the oxidation byoxygen in the exhaust gas stream of unburned hydrocarbons and carbonmonoxide as well as the reduction of nitrogen oxides to nitrogen.Government regulations (such as LEVIII in the US and Euro 6 & 7 inEurope) are targeting emissions during cold start and before thecatalyst has fully warmed up. One strategy to address this is to ensureplatinum group metals (PGMs) are delivered by supports that do notinterfere with and that enhance performance of PGMs at lowertemperatures.

A catalyst with lanthanide-doped zirconia as a support for TWCapplications is presented in U.S. Patent Appln. Pub. No. 2013/0115144.WO9205861 discusses a co-formed ceria-zirconia composite to be used tosupport rhodium where a base metal oxide may be co-dispersed onto thesupport with the rhodium as a promoter.

There is a continuing need in the art to provide catalytic articles thatprovide excellent catalytic activity and/or light-off performance and/orefficient use of components to achieve regulated emissions.

SUMMARY

Provided are composites of mixed metal oxides for an exhaust gaspurifying catalyst, and methods of making and using the same. Thesecomposites are effective as supports for platinum group metals (PGMs),in particular rhodium.

A first aspect provides composites of mixed metal oxides for an exhaustgas purifying catalyst, the composites comprising, by weight: zirconiain an amount in the range of 55-99%; titania in an amount in the rangeof 1-25%; a promoter and/or a stabilizer in an amount in the range of0-20%. The promoter may comprise a rare earth metal oxide and is presentin an amount in the range of 0.1-20%. The promoter may compriselanthana, tungsta, ceria, neodymia, gadolinia, yttria, praseodymia,samaria, hafnia, or combinations thereof. The stabilizer may be presentin an amount in the range of 0.1-5% and comprise silicon oxide. Thestabilizer may be present in an amount in the range of 0.1-10% andcomprise an alkaline earth metal oxide. The ceria content of thecomposite may be 20% or less by weight, or 10% or less, or 5% or less,or 1% or less, or 0.1% or less, or even 0%.

The composite may comprise the zirconia, the titania, and the promoterand/or the stabilizer all in a co-precipitated state. Or, the compositemay comprise the zirconia and the promoters and/or stabilizers in aco-precipitated state and the titania is impregnated from a titaniaprecursor. The titania precursor may comprise a titanium salt, atitanium-containing organic complex, a titania sol, or colloidaltitania.

The composite may have a surface area in the range of 10-40 m²/g afteroven aging for 12 hours at 1000° C.

Another aspect provides catalyst composites for treatment of an exhauststream of a combustion engine, the catalyst composites comprising acatalytic material on a carrier, the catalytic material comprising: aplatinum group metal (PGM) supported on any of the mixed metal oxidecomposites disclosed herein. The catalyst composites may comprise arhodium in an amount in the range of 0.1 to 5% by weight. The catalystcomposites may comprise a titania to rhodium weight ratio in the rangeof 5 to 250. The catalyst composites may comprises 0.25% by weightrhodium, which after aging at 950° C. is effective to provide conversionof 50% or more of carbon monoxide and nitrogen oxides; and conversion of10% or more of hydrocarbons at lambdas in the range of 0.98 to 1.02during a lean-rich lambda sweep test at 300° C.

In a further aspect, a system for treatment of an exhaust streamincluding hydrocarbons, carbon monoxide, and nitrogen oxides of aninternal combustion engine comprises: an exhaust conduit in fluidcommunication with the internal combustion engine via an exhaustmanifold; and any catalyst composite disclosed herein.

In another aspect, a method for treating exhaust gases comprisescontacting a gaseous stream comprising hydrocarbons, carbon monoxide,and nitrogen oxides with any catalyst composite disclosed herein. Themixed metal oxide composite may comprise, by weight: zirconia in anamount in the range of 55-90%; titania in an amount in the range of5-25%; a promoter comprising lanthanum oxide in an amount in the rangeof 5-20% and the platinum group metal comprises rhodium in an amount of0.25%; and after aging at 950° C., the catalyst composite may beeffective to provide conversion of 50% or more of carbon monoxide andnitrogen oxides; and conversion of 10% or more of hydrocarbons atlambdas in the range of 0.98 to 1.02 during a lean-rich lambda sweeptest at 300° C.

Also provided are methods of making a composite of mixed metal oxidescomprising: obtaining or forming a first aqueous solution of a salt ofzirconium, a salt of a metal promoter, and, optionally, a salt of astabilizer; obtaining or forming a second aqueous solution of a salt oftitanium; mixing the first and second aqueous solutions; andco-precipitating the zirconia, the optional metal of the promoter orstabilizer, and the titania under basic conditions; thereby forming aco-precipitated mixed metal oxide composite. The method may furthercomprise drying and calcining the co-precipitated mixed metal oxidecomposite.

Also provided are methods of making a composite of mixed metal oxidescomprising: obtaining a co-precipitated zirconia and metal promoter andoptional stabilizer; obtaining an aqueous solution of a precursor oftitanium; impregnating the co-precipitated zirconia and metal promoterwith the precursor of titanium; thereby forming a mixed metal oxidecomposite.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure may be more completely understood in consideration of thefollowing detailed description of various embodiments of the disclosurein connection with the accompanying drawings, in which:

FIG. 1 provides a graph of carbon monoxide (CO) conversion versus lambdaat 300° C.;

FIG. 2 provides a graph of hydrocarbon (HC) conversion versus lambda at300° C.;

FIG. 3 provides a graph of nitrogen oxides (NO) conversion versus lambdaat 300° C.;

FIG. 4 provides a graph of hydrocarbon (HC) conversion versus lambda at350° C.; and

FIG. 5 provides a graph of carbon monoxide (CO) conversion versus lambdaat 350° C.;

DETAILED DESCRIPTION

Composites of mixed metal oxides comprise, by weight of the composite:zirconia in an amount in the range of 55-99%; titania in an amount inthe range of 1-25%; a promoter and/or a stabilizer in an amount in therange of 0-20%, which are effective as a support for a platinum groupmetal (PGM). PGMs, in particular rhodium, are supported thereon in awashcoat, which is coated onto a carrier for use as an catalystcomposite or article for treatment downstream of a combustion engine,for example, an automotive engine.

The following definitions are used herein.

A platinum group metal (PGM) component refers to any compound thatincludes a PGM. For example, the PGM may be in metallic form—zerovalance, or the PGM may be in an oxide form. Reference to PGM componentallows for the presence of the PGM in any valance state. For example,rhodium may be present in Rh⁰ and/or Rh³⁺, or any other oxidationstates.

“BET surface area” has its usual meaning of referring to theBrunauer-Emmett-Teller method for determining surface area byN₂-adsorption measurements. Unless otherwise stated, “surface area”refers to BET surface area.

“Support” in a catalytic material or catalyst washcoat refers to amaterial that receives precious metals, stabilizers, promoters, binders,and the like through precipitation, association, dispersion,impregnation, or other suitable methods. The composites of mixed metaloxides comprising zirconia, titania, and optionally promoters and/orstabilizers disclosed herein are effective as supports. Examples ofother supports include, but are not limited to, refractory metal oxides,including high surface area refractory metal oxides, compositescontaining oxygen storage components, and the mixed metal oxidesdisclosed herein.

“Transition metal oxides” (TMOs) refer to one or more oxides of themetals of Groups 3-12 of the Periodic Table of Elements.

“Refractory metal oxide supports” include bulk alumina, ceria, zirconia,titania, silica, magnesia, neodymia, and other materials are known forsuch use. Such materials are considered as providing durability to theresulting catalyst.

“High surface area refractory metal oxide supports” refer specificallyto support particles having pores larger than 20 Å and a wide poredistribution. High surface area refractory metal oxide supports, e.g.,alumina support materials, also referred to as “gamma alumina” or“activated alumina,” typically exhibit a BET surface area of freshmaterial in excess of 60 square meters per gram (“m²/g”), often up toabout 200 m²/g or higher. Such activated alumina is usually a mixture ofthe gamma and delta phases of alumina, but may also contain substantialamounts of eta, kappa and theta alumina phases.

“Rare earth metal oxides” refer to one or more oxides of scandium,yttrium, and the lanthanum series defined in the Periodic Table ofElements. Rare earth metal oxides can be both exemplary oxygen storagecomponents and promoter materials. Examples of suitable oxygen storagecomponents include ceria, praseodymia, or combinations thereof. Deliveryof ceria can be achieved by the use of, for example, ceria, a mixedoxide of cerium and zirconium, and/or a mixed oxide of cerium,zirconium, and other rare earth element(s). Suitable promoters includeone or more non-reducible oxides of one or more rare earth metalsselected from the group consisting of lanthanum, tungsten, cerium,neodymium, gadolinium, yttrium, praseodymium, samarium, hafnium, andmixtures thereof.

“Alkaline earth metal oxides” refer to Group II metal oxides, which areexemplary stabilizer materials. Suitable stabilizers include one or morenon-reducible metal oxides wherein the metal is selected from the groupconsisting of barium, calcium, magnesium, strontium and mixturesthereof. Preferably, the stabilizer comprises one or more oxides ofbarium and/or strontium.

“Washcoat” is a thin, adherent coating of a catalytic or other materialapplied to a refractory substrate, such as a honeycomb flow throughmonolith substrate or a filter substrate, which is sufficiently porousto permit the passage there through of the gas stream being treated. A“washcoat layer,” therefore, is defined as a coating that is comprisedof support particles. A “catalyzed washcoat layer” is a coatingcomprised of support particles impregnated with catalytic components.

Mixed Metal Oxide Support Materials

Ti—La—ZrO₂ support materials are prepared as follows. One exemplarymethod is to co-precipitate desired ingredients: titanium and zirconiumand any desired promoters. Another exemplary method is to provide aco-precipitated zirconia composite (except a Ce—Zr, for example, aLa—ZrO₂) and then impregnate with a titanium precursor.

A co-precipitate of all desired material is prepared by preparing twosolutions. A first aqueous solution comprises a salt of zirconium salt(for example, zirconium nitrate). A second aqueous solution comprises asalt of lanthanum (for example, lanthanum nitrate) and a titaniaprecursor. The solutions were added to an aqueous solution of ammonia(NH₃), and the mixture was held at a pH of ˜9.0. A filtrate is obtainedby drying and treating with an acid such as lauric acid. Furtherwashing, drying, and calcining of the filtrate is conducted to obtain athe desired composite. Zirconia is generally going to be present in anamount in the range of 55-99 wt-%; titania in an amount in the range of1-25 wt-%; and optionally a promoter and/or a stabilizer in an amount inthe range of 0-20 wt-%.

In another method, the composite material can also be made byimpregnation of a titania precursor (a titanium compound or titania sol)on a high surface area co-precipitated La-stabilized zirconia composite.

The support materials may be characterized in many ways. For example,crystal form of the titanium may be determined by X-Ray Diffraction(XRD). Surface area of fresh support materials may be in the range of60-90 m²/g. Aged support materials may have a surface area in the rangeof 10-40 m²/g after oven aging for 12 hours at 1000° C. The weight ratioof titania to rhodium may be in the range of 5 to 250.

Catalytic Materials

Catalytic materials are prepared as follows. A desired platinum groupmetal (PGM) is supported on the Ti—La—ZrO₂ support by methods known inthe art, for example, impregnated incipient wetness techniques.

Catalyst Composites

Once the catalytic materials are prepared, a catalyst composite may beprepared in one or more layers on a carrier. A dispersion of any of thecatalytic materials as described herein may be used to form a slurry fora washcoat.

To the slurry may be added any desired additional ingredients such asother platinum group metals, other supports, other stabilizers andpromoters, and one or more oxygen storage components.

In one or more embodiments, the slurry is acidic, having a pH of about 2to less than about 7. The pH of the slurry may be lowered by theaddition of an adequate amount of an inorganic or an organic acid to theslurry. Combinations of both can be used when compatibility of acid andraw materials is considered. Inorganic acids include, but are notlimited to, nitric acid. Organic acids include, but are not limited to,acetic, propionic, oxalic, malonic, succinic, glutamic, adipic, maleic,fumaric, phthalic, tartaric, citric acid and the like. Thereafter, ifdesired, water-soluble or water-dispersible compounds of oxygen storagecomponents, e.g., cerium-zirconium composite, a stabilizer, e.g., bariumacetate, and a promoter, e.g., lanthanum nitrate, may be added to theslurry. The slurry may thereafter comminuted to result in substantiallyall of the solids having particle sizes of less than about 20 microns,i.e., between about 0.1-15 microns, in an average diameter. Thecomminution may be accomplished in a ball mill or other similarequipment, and the solids content of the slurry may be, e.g., about10-50 wt. %, more particularly about 10-40 wt. %. The carrier may thenbe dipped one or more times in such slurry or the slurry may be coatedon the carrier such that there will be deposited on the carrier thedesired loading of the washcoat/metal oxide composite, e.g., about 0.5to about 3.0 g/in³.

Thereafter the coated carrier is calcined by heating, e.g., at 500-600°C. for about 1 to about 3 hours.

Typically, when platinum group metal is desired, a metal component isutilized in the form of a compound or complex to achieve dispersion ofthe component on a refractory metal oxide support, e.g., activatedalumina or a ceria-zirconia composite. For the purposes herein, the term“metal component” means any compound, complex, or the like which, uponcalcination or use thereof, decomposes or otherwise converts to acatalytically active form, usually the metal or the metal oxide.Water-soluble compounds or water-dispersible compounds or complexes ofthe metal component may be used as long as the liquid medium used toimpregnate or deposit the metal component onto the refractory metaloxide support particles does not adversely react with the metal or itscompound or its complex or other components which may be present in thecatalyst composition and is capable of being removed from the metalcomponent by volatilization or decomposition upon heating and/orapplication of a vacuum. In some cases, the completion of removal of theliquid may not take place until the catalyst is placed into use andsubjected to the high temperatures encountered during operation.Generally, both from the point of view of economics and environmentalaspects, aqueous solutions of soluble compounds or complexes of theprecious metals are utilized. During the calcination step, or at leastduring the initial phase of use of the composite, such compounds areconverted into a catalytically active form of the metal or a compoundthereof.

Additional layers may be prepared and deposited upon previous layers inthe same manner as described above for deposition any layer upon thecarrier.

Carrier

In one or more embodiments, the catalytic material is disposed on acarrier.

The carrier may be any of those materials typically used for preparingcatalyst composites, and will preferably comprise a ceramic or metalhoneycomb structure. Any suitable carrier may be employed, such as amonolithic substrate of the type having fine, parallel gas flow passagesextending therethrough from an inlet or an outlet face of the substrate,such that passages are open to fluid flow therethrough (referred to ashoneycomb flow through substrates). The passages, which are essentiallystraight paths from their fluid inlet to their fluid outlet, are definedby walls on which the catalytic material is coated as a washcoat so thatthe gases flowing through the passages contact the catalytic material.The flow passages of the monolithic substrate are thin-walled channels,which can be of any suitable cross-sectional shape and size such astrapezoidal, rectangular, square, sinusoidal, hexagonal, oval, circular,etc. Such structures may contain from about 60 to about 900 or more gasinlet openings (i.e., cells) per square inch of cross section.

The carrier can also be a wall-flow filter substrate, where the channelsare alternately blocked, allowing a gaseous stream entering the channelsfrom one direction (inlet direction), to flow through the channel wallsand exit from the channels from the other direction (outlet direction).A dual oxidation catalyst composition can be coated on the wall-flowfilter. If such a carrier is utilized, the resulting system will be ableto remove particulate matters along with gaseous pollutants. Thewall-flow filter carrier can be made from materials commonly known inthe art, such as cordierite or silicon carbide.

The carrier may be made of any suitable refractory material, e.g.,cordierite, cordierite-alumina, silicon nitride, zircon mullite,spodumene, alumina-silica magnesia, zircon silicate, sillimanite, amagnesium silicate, zircon, petalite, alumina, an aluminosilicate andthe like.

The carriers useful for the catalysts of the present invention may alsobe metallic in nature and be composed of one or more metals or metalalloys. The metallic carriers may be employed in various shapes such ascorrugated sheet or monolithic form. Preferred metallic supports includethe heat resistant metals and metal alloys such as titanium andstainless steel as well as other alloys in which iron is a substantialor major component. Such alloys may contain one or more of nickel,chromium and/or aluminum, and the total amount of these metals mayadvantageously comprise at least 15 wt % of the alloy, e.g., 10-25 wt %of chromium, 3-8 wt % of aluminum and up to 20 wt % of nickel. Thealloys may also contain small or trace amounts of one or more othermetals such as manganese, copper, vanadium, titanium and the like. Thesurface of the metal carriers may be oxidized at high temperatures,e.g., 1000° C. and higher, to improve the resistance to corrosion of thealloys by forming an oxide layer on the surfaces of the carriers. Suchhigh temperature-induced oxidation may enhance the adherence of therefractory metal oxide support and catalytically promoting metalcomponents to the carrier.

In alternative embodiments, one or more catalyst compositions may bedeposited on an open cell foam substrate. Such substrates are well knownin the art, and are typically formed of refractory ceramic or metallicmaterials.

Before describing several exemplary embodiments of the invention, it isto be understood that the invention is not limited to the details ofconstruction or process steps set forth in the following description.The invention is capable of other embodiments and of being practiced invarious ways. In the following, preferred designs are provided,including such combinations as recited used alone or in unlimitedcombinations, the uses for which include catalysts, systems, and methodsof other aspects of the present invention.

Embodiments

Various embodiments are listed below. It will be understood that theembodiments listed below may be combined with all aspects and otherembodiments in accordance with the scope of the invention.

Embodiment one is a composite of mixed metal oxides for an exhaust gaspurifying catalyst, comprising zirconia, titania, and a promoter and/ora stabilizer.

Embodiment two is a catalyst composite for treatment of an exhauststream of a combustion engine, the catalyst composites comprising acatalytic material on a carrier, the catalytic material comprising: aplatinum group metal (PGM) supported on any of the mixed metalcomposites disclosed herein.

Embodiment three is a system for treatment of an exhaust streamincluding hydrocarbons, carbon monoxide, and nitrogen oxides of aninternal combustion engine comprising: an exhaust conduit in fluidcommunication with the internal combustion engine via an exhaustmanifold; and any of the catalyst composites disclosed herein.

Embodiment four is a method for treating exhaust gases comprisescontacting a gaseous stream comprising hydrocarbons, carbon monoxide,and nitrogen oxides with any the catalyst composites disclosed herein.

Embodiment five is a method of making a composite of mixed metal oxidescomprising: obtaining or forming a first aqueous solution of a salt ofzirconium, a salt of a metal promoter, and, optionally, a salt of astabilizer; obtaining or forming a second aqueous solution of a salt oftitanium; mixing the first and second aqueous solutions; andco-precipitating the zirconium, the optional metal of the promoter orstabilizer, and the titanium under basic conditions; thereby forming aco-precipitated mixed metal oxide composite.

Embodiment six is a method of making a composite of mixed metal oxidescomprising: obtaining a co-precipitated zirconia and metal promoter andoptional stabilizer; obtaining an aqueous solution of a precursor oftitanium; impregnating the co-precipitated zirconia and metal promoterwith the precursor of titanium; thereby forming a co-precipitated mixedmetal oxide composite.

Each of embodiments one through six herein may have the following designfeatures, alone or in combination:

the mixed metal oxide composites may comprise, by weight: zirconia in anamount in the range of 55-99%; titania in an amount in the range of1-25%; a promoter and/or a stabilizer in an amount in the range of0-20%;

the promoter may comprise a rare earth metal oxide and is present in anamount in the range of 0.1-20%;

the promoter may comprise lanthana, tungsta, ceria, neodymia, gadolinia,yttria, praseodymia, samaria, hafnia, or combinations thereof;

the stabilizer may be present in an amount in the range of 0.1-5% andcomprise silicon oxide;

the stabilizer may be present in an amount in the range of 0.1-10% andcomprise an alkaline earth metal oxide;

the ceria content of the mixed metal oxide composite may be 20% or lessby weight, or 10% or less, or 5% or less, or 1% or less, or 0.1% orless, or even 0%;

the mixed metal oxide composite may comprise the zirconia, the titania,and the promoter and/or the stabilizer all in a co-precipitated state;

the mixed metal oxide composite may comprise the zirconia and thepromoters and/or stabilizers in a co-precipitated state and the titaniais impregnated from a titania precursor;

the titania precursor may comprise a titanium salt, atitanium-containing organic complex, a titania sol, or colloidaltitania;

the mixed metal oxide composite may have a surface area in the range of10-40 m²/g after oven aging for 12 hours at 1000° C.

the catalyst composites may comprise a rhodium in an amount in the rangeof 0.1 to 5% by weight and the wt. % is based on the total weight of thecomposite;

the catalyst composites may comprise a titania to rhodium weight ratioin the range of 5 to 250;

the catalyst composites may comprises 0.1 to 5% by weight of rhodium,for example 0.25% by weight rhodium, which after aging at 950° C. iseffective to provide conversion of 50% or more of carbon monoxide,nitrogen oxides, and hydrogen; and conversion of 10% or more ofhydrocarbons at lambdas in the range of 0.98 to 1.02 during a lean-richlambda sweep test at 300° C.;

the mixed metal oxide composite may comprise, by weight: zirconia in anamount in the range of 55-90%; titania in an amount in the range of5-25%; a promoter comprising lanthanum oxide in an amount in the rangeof 5-20% and the platinum group metal comprises rhodium in an amount of0.25%; and after aging at 950° C., the catalyst composite may beeffective to provide conversion of 50% or more of carbon monoxide,nitrogen oxides, and hydrogen; and conversion of 10% or more ofhydrocarbons at lambdas in the range of 0.98 to 1.02 during a lean-richlambda sweep test at 300° C.; and

the methods may further comprise drying and calcining theco-precipitated mixed metal oxide composite.

EXAMPLES

The following non-limiting examples shall serve to illustrate thevarious embodiments of the present invention. In each of the examples,the carrier was cordierite.

Example 1

An exemplary mixed metal oxide comprising by weight 5% titania (TiO₂) asa transition metal oxide (TMO), 5% lathana as a stabilizer/dopant, andbalanced with zirconia (main component) (Ti—La—ZrO₂) was prepared asfollows. An aqueous solution of zirconium nitrate was prepared to formsolution 1. An aqueous solution of lanthanum nitrate was prepared, towhich a precursor of titania (Ti—(V)-ethoxide) was added to formsolution 2. Solutions 1 and 2 were added to an aqueous solution ofammonia (NH₃) and the mixture was held at a pH of ˜9.0 for 15 minutesunder mixing conditions. The mixture was divided and dried in anautoclave for 12 hours at 150° C. Lauric acid was added to increase thesurface area of the final product. A filtrate was obtained using afilter, which was then washed with ammonia (25% solution) to remove thenitrates. The filtrate was then dried at 40° C. and calcined at 700° C.

The composite was tested for surface area using the BET method. Thefresh composite had a surface area of 70 m²/g and an aged composite(1000° C. for 12 hours oven aging) had a surface area of 15 m²/g.

Example 2 Comparative

For comparison, a 10 wt.-% lanthana and 90 wt.-% zirconia composite(La—ZrO₂) made the same way as the Ti—La—ZrO₂ composite of Example 1.The comparative composite was tested for surface area using the sametest method used in Example 1. The comparative composite had a freshsurface area of 83 m²/g and an aged composite (1000° C. for 12 hoursoven aging) surface area of 25 m²/g.

Example 3

Catalytic material was prepared comprising rhodium (Rh) supported on theTi—La—ZrO₂composite of Example 1. Specifically, a 0.25 wt % Rh nitratesolution was impregnated onto the composite using standard incipientwetness techniques. This material was dried at 120° C. and then calcinedat 550° C. for 1 hour in air. For testing purposes, the catalyticmaterial was shaped by slurrying with zirconium acetate (5 wt % on thecomposite), drying under stirring, calcining at 550° C. for 2 hours inair, and crushing/sieving to 250-500 μm. The shaped catalytic materialwas aged at 950° C. for 5 hours in 10% water under lean rich cycle.

Example 4 Comparative

A comparative catalytic material was prepared comprising rhodium (Rh)supported on the La—ZrO₂composite of Comparative Example 2.Specifically, a 0.25 wt % Rh nitrate solution was impregnated onto thecomposite using standard incipient wetness techniques. This material wasdried at 120° C. and then calcined at 550° C. for 1 hour in air. Fortesting purposes, the catalytic material was shaped by slurrying withzirconium acetate (5 wt % on the composite), drying under stirring,calcining at 550° C. for 2 hours in air, and crushing/sieving to 250-500μm. The shaped catalytic material was aged at 950° C. for 5 hours in 10%water under lean rich cycle.

Example 5 Testing

The aged catalytic materials of Example 3 and Comparative Example 4 weretested under a lambda sweep protocol at different temperatures (250,300, 350, and 450° C.). Conditions were: GHSV=70000 h−1 (normalized to 1mL coated catalyst) and oscillating feed (λavg±0.05, 1 sec lean, 1 secrich, 180 sec/position).

At 300° C., the catalytic material using Ti—La—ZrO₂ composite of Example1 showed superior performance as compared to a catalytic material usinga commercially available La—Zr composite. For higher temperatures, theperformances of the different catalytic materials were not significant.Effective performance at below 350-400° C. is desired to help loweremissions during cold-start and to boost light-off performance. FIGS.1-3 show the emissions conversions (carbon monoxide (CO), hydrocarbon(HC), and nitrogen oxides (NO)) for the catalytic materials of Example 3and Comparative Example 4 at 300° C.

Example 6

A formulated automotive catalyst composite comprising catalytic materialcomprising two layers on a carrier was prepared. The total preciousmetal loading was 60 g/ft³ and with a Pt/Pd/Rh ratio of 0/55/5. Thesubstrate had a cell density of 600 cells per square inch and with wallthickness of approximately 4 mil (or 101.6 μm). The size of thesubstrate was 4.66×3 inches and the volume was 51.17 in³.

A bottom layer deposited on the carrier comprised palladium (Pd), aportion of which was supported by a ceria-zirconia oxygen storagecomponent (OSC) and another portion of which was supported by a highsurface area gamma-alumina support. The bottom layer also containedbaria and zirconia. The loading of the bottom layer was 2.332 g/in³.

A top layer deposited on the bottom layer comprised the rhodium (Rh) ona support that comprised 5% TiO₂ impregnated onto a commercial La—ZrO₂having a lanthana content of 9 wt-%. The loading of the top layer was1.403 g/in³.

Example 7 Comparative

A comparative formulated automotive catalyst composite comprisingcatalytic material comprising two layers on a carrier was prepared. Thetotal precious metal loading was 60 g/ft³ and with a Pt/Pd/Rh ratio of0/55/5. The substrate had a cell density of 600 cells per square inchand with wall thickness of approximately 4 mil (or 101.6 μm). The sizeof the substrate was 4.66×3 inches and the volume was 51.17 in³.

A bottom layer deposited on the carrier comprised palladium (Pd), aportion of which was supported by a ceria-zirconia oxygen storagecomponent (OSC) and another portion of which was supported by a highsurface area gamma-alumina support. The bottom layer also containedbaria and zirconia. The loading of the bottom layer was 2.332 g/in³.

A top layer deposited on the bottom layer comprised the rhodium (Rh) ona commercial La—ZrO₂ support having a lanthana content of 9 wt-%. Theloading of the top layer was 1.403 g/in³.

Example 8 Testing

The formulated catalyst composites of Example 6 and Comparative Example7 were aged at 950° C. for 5 hours in 10% water under lean/rich cycles.The aged composites were tested under a lambda sweep protocol atdifferent temperatures (300, 350, and 450° C.). Conditions were:GHSV=125000 h−1 (normalized to 1 mL coated catalyst) and oscillatingfeed (λavg±0.025, 0.5 sec lean, 0.5 sec rich, 50 sec/position).

The catalyst composite of Example 6 showed an advantage for conversionof hydrocarbons (HC) at 300-350° C. FIG. 4 shows the emissionsconversion of hydrocarbon (HC) for the formulated catalyst composites ofExample 6 and Comparative Example 7 at 300-350° C.—especially under richconditions. At 400° C. or above, there was not a significant advantage.As shown in FIG. 5, for carbon monoxide (CO) conversion, the catalystcomposite of Example 6 showed an improvement at 300-350° C. For nitrogenoxides (NO) conversions, there was not a significant difference, but itis noted that the catalyst testing method itself may be a contributingfactor, i.e., NOx conversion is too high to differentiate the differentbetween the two catalysts, not the difference in support materials.

Reference throughout this specification to “one embodiment,” “certainembodiments,” “one or more embodiments” or “an embodiment” means that aparticular feature, structure, material, or characteristic described inconnection with the embodiment is included in at least one embodiment ofthe invention. Thus, the appearances of the phrases such as “in one ormore embodiments,” “in certain embodiments,” “in one embodiment” or “inan embodiment” in various places throughout this specification are notnecessarily referring to the same embodiment of the invention.Furthermore, the particular features, structures, materials, orcharacteristics may be combined in any suitable manner in one or moreembodiments.

While this invention has been described with an emphasis upon preferredembodiments, it will be obvious to those of ordinary skill in the artthat variations in the preferred devices and methods may be used andthat it is intended that the invention may be practiced otherwise thanas specifically described herein. Accordingly, this invention includesall modifications encompassed within the spirit and scope of theinvention as defined by the claims that follow.

1-18. (canceled)
 19. A method of making a composite of mixed metaloxides comprising: obtaining or forming a first aqueous solution of asalt of zirconium, a salt of a metal promoter, and, optionally, a saltof a stabilizer; obtaining or forming a second aqueous solution of asalt of titanium; mixing the first and second aqueous solutions; andco-precipitating the zirconium, the optional metal of the promoter orstabilizer, and the titanium under basic conditions; thereby forming aco-precipitated mixed metal oxide composite.
 20. The method of claim 19,wherein the co-precipitated composite of mixed metal oxides comprises byweight of the composite: zirconia in an amount in the range of 55-99%;titania in an amount in the range of 1-25%; a promoter and/or astabilizer in an amount in the range of 0-20%.
 21. The method of claim19, further comprising drying and calcining the co-precipitated mixedmetal oxide composite.
 22. A method of making a composite of mixed metaloxides comprising: obtaining a co-precipitated zirconia and metalpromoter and optional stabilizer; obtaining an aqueous solution of aprecursor of titanium; impregnating the co-precipitated zirconia andmetal promoter with the precursor of titanium; thereby forming a mixedmetal oxide composite.
 23. The method of claim 22, wherein the mixedmetal oxide composite comprises by weight of the composite: zirconia inan amount in the range of 55-99%; titania in an amount in the range of1-25%; a promoter and/or a stabilizer in an amount in the range of0-20%.